Photoelectric coupling assembly and manufacturing method thereof

ABSTRACT

A photoelectric coupling assembly and manufacturing method thereof enabling a three dimensional electrical wiring pattern is provided. The assembly includes a photoelectric conversion unit equipped with a photoelectric conversion element and a molded article. The molded article has a hole configured and arranged to have an optical fiber inserted there-through such that a distal end of the fiber faces an active layer of the conversion element, a front surface on which the conversion unit is mounted, and a side surface being contiguous to the front surface. The lead being insert molded into the molded article has a first surface being exposed at the front surface and electrically connected to the conversion element, a second surface being exposed at the side surface, and an engaging portion having a width increasing in a direction away from the front surface. At least a portion of the engaging portion is contained inside the resin forming the molded article.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of and claims priority to U.S. patentapplication Ser. No. 11/866,596, filed on Oct. 3, 2007, which claimspriority to Japanese Patent Application No. 2006-284845, filed on Oct.19, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photoelectric coupling assembly forconnecting an electrical circuit and an optical fiber and a method formanufacturing the photoelectric coupling assembly.

2. Description of the Background Arts

With the development of broadband communication systems, higher speedsand larger capacities are increasingly in demand for networked householdelectric appliances as well as for routers at network nodes.Consequently, the investigation and implementation of opticalinterconnections is on the rise. An optical interconnection is aconnection arrangement contrived to carry out a photoelectric conversionat a boundary section (interface) between a signal processing sectionand a signal transmission section such that the broadband capacity ofoptical fiber technology can be utilized to accomplish high-speed,high-capacity transmissions. Japanese Laid-Open Patent ApplicationPublication No. 2005-43622, for example, discloses a technique in whichan electrical circuit and an optical fiber are coupled together at aphotoelectric conversion section using a photoelectric coupling assemblythat includes a photoelectric conversion element (a light-emittingelement or a light-receiving element) and an optical fiber holdingmember.

FIG. 11 is a cross sectional view showing the assembled state of anoptical fiber cable connected to a photoelectric coupling assembly inaccordance with the disclosure of Japanese Laid-Open Patent ApplicationPublication No. 2005-43622. The photoelectric coupling assembly 100includes a molded article 104 having holding holes 102 each configuredto mechanically hold an optical fiber 101 such that an opticalinput/output end surface 103 of each optical fiber 101 is exposed at amain surface. An electrical wiring pattern 105 is provided on the mainsurface and a side surface of the molded article 104 such that theportion of the electrical wiring pattern 105 on the main surface isconnected to the portion of the electrical wiring pattern 105 on theside surface. A photo-semiconductor element 107 is provided in front ofthe optical fiber 101 with an insulating film 106 disposedthere-between. The photo-semiconductor element 107 is connected to theelectrical wiring pattern 105 with bumps 108. The same patentpublication claims that the degree of freedom with which thephoto-electric coupling assembly can be arranged is increased by havingthe kind of electrical wiring pattern just described. However, it isinherently difficult to form an electrical wiring pattern in acontinuous manner on the surface of an object such that the wiringpattern is accurately positioned in three dimensions.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a photoelectriccoupling assembly and a manufacturing method thereof that are contrivedsuch that the electrical wiring pattern can be positioned accurately inthree dimensions.

In order to achieve the object, the invention provides a photoelectriccoupling assembly that comprises: (1) a photoelectric conversion unitequipped with a photoelectric conversion element; and (2) a moldedarticle. The molded article includes a front surface on which thephotoelectric conversion unit is mounted and an optical fiber insertionhole configured and arranged to have an optical fiber insertedthere-through such that a distal end of the optical fiber faces anactive layer of the photoelectric conversion element. A lead is insertmolded into the molded article. The lead has a first surface that isexposed at the front surface of the molded article and electricallyconnected to the photoelectric conversion element, a second surface thatis exposed at a side surface of the molded article that continuouslyadjoins the front surface of the molded article, and an engaging portionhaving a width that increases in a direction away from the front surfaceof the molded article. At least a portion of the engaging portion iscontained inside the resin that forms the molded article. The “width” ofthe lead is the dimension of the lead in a direction perpendicular tothe lengthwise direction of the lead and the direction away from thefront surface of the molded article.

Another aspect of the present invention provides a method formanufacturing a photoelectric coupling assembly that comprises: (1) aphotoelectric conversion unit equipped with a photoelectric conversionelement; and (2) a molded article equipped with an optical fiberinsertion hole that is configured and arranged to have an optical fiberinserted there-through such that a distal end of the optical fiber facesan active layer of the photoelectric conversion element, a front surfaceon which the photoelectric conversion unit is mounted, and a lead thatis electrically connected to the photoelectric conversion element andhas an engaging portion having a width that increases in a directionaway from the front surface of the molded article. In this manufacturingmethod, (1) a lead frame is insert molded to the front surface of themolded article such that the engaging portion is contained inside theresin forming the molded article and a first surface of the lead isexposed at the front surface of the molded article and (2) the leadframe is cut such that a second surface of the lead is exposed at a sidesurface of the molded article that contiguously adjoins the frontsurface of the molded article.

In a photoelectric coupling assembly and manufacturing method thereofaccording to the present invention, it is acceptable to form theengaging portion by using etching to form a lead forming pattern in thelead frame. It is also acceptable for the lead to be configured suchthat a thickness thereof varies. The thickness variation of the lead canbe formed by etching or plating. It is acceptable for a width of thefirst surface to vary with respect to a direction perpendicular to thewidth. The “thickness” of the lead is the longitudinal dimension of thelead in a direction perpendicular to the front surface of the moldedarticle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a molded article of a photoelectriccoupling assembly in accordance with an embodiment of the presentinvention.

FIG. 2 is a partial cross sectional view of the photoelectric couplingassembly at the section line II-II in FIG. 1 and shows the distal end ofthe photoelectric coupling assembly.

FIG. 3 is a top plan view of a lead frame used in a photoelectriccoupling assembly in accordance with the present invention.

FIGS. 4A and 4B are cross sectional views showing examples of leads usedin a photoelectric coupling assembly in accordance with the presentinvention.

FIGS. 5A and 5B are cross sectional views showing the insert moldedstates of the leads shown in FIGS. 4A and 4B.

FIGS. 6A and 6B are cross sectional views showing examples of leads withplated surfaces used in a photoelectric coupling assembly in accordancewith the present invention.

FIG. 7 is a longitudinal cross sectional view of a molded article of aphotoelectric coupling assembly in accordance an embodiment of thepresent invention. The cross section lies in a plane that is parallel toan optical fiber insertion hole and includes a lead.

FIGS. 8A and 8B are cross sectional views showing other examples ofleads used in a photoelectric coupling assembly in accordance with thepresent invention.

FIGS. 9A and 9B are frontal views showing other examples of leads usedin a photoelectric coupling assembly in accordance with the presentinvention as seen from the front surface of the molded article.

FIG. 10 is a cross sectional view illustrating a photoelectric couplingassembly being insert molded in accordance with an embodiment of amanufacturing method for a photoelectric coupling assembly in accordancewith the present invention.

FIG. 11 is a cross sectional view showing a conventional photoelectriccoupling assembly with optical fibers assembled thereto.

DETAILED DESCRIPTION OF THE INVENTION

The above-mentioned features and other features, aspects, and advantagesof the present invention will be better understood through the followingdescription, appended claims, and accompanying drawings. In theexplanation of the drawings, identical reference numerals are applied toidentical elements and duplicate explanations are omitted.

FIG. 1 is a perspective view of a molded article of a photoelectriccoupling assembly in accordance with an embodiment of the presentinvention. The photoelectric coupling assembly 10 includes a main unit(molded article) 20 whose overall shape is generally cuboids and aphotoelectric conversion unit 40 that is mounted to a front surface 21of the main unit 20. The main unit 20 has a plurality of optical fiberinsertion holes 24, each of which is configured and arranged to receivean optical fiber 11 there-through with a distal end 11 b of the opticalfiber facing an active layer of a photoelectric conversion element ofthe photoelectric conversion unit 40. The main unit 20 also has a frontsurface 21 on which the photoelectric conversion unit 40 is mounted. Anelectrical wiring pattern section 23 is provided across the frontsurface 21 of the main unit 20 and a side surface 22 (e.g., top andbottom surfaces) that is contiguous with the front surface 21. Theelectrical wiring pattern section 23 comprises alternately arrangedshort electrical wires 23 a and long electrical wires 23 b. The opticalfiber insertion holes 24 are arranged between the short electrical wires23 a.

FIG. 2 is a partial cross sectional view of the photoelectric couplingassembly 10 at the section line II-II in FIG. 1 and shows the distal endof the photoelectric coupling assembly 10. The photoelectric conversionunit 40 has a photoelectric conversion element 41 and an active layer 42of the photoelectric conversion unit 40 is positioned so as to face theoptical fiber insertion holes 24 of the main unit 20. The photoelectricconversion unit 40 is provided with electrodes 43 for supplyingelectricity to the active layer 42 or transmitting a signal from theactive layer 42. When the photoelectric conversion unit 40 is mounted tothe front surface 21 of the main unit 20, the electrodes 43 contact theelectrical wiring pattern section 23 of the main unit 20.

FIG. 3 is a top plan view of a lead frame used in a photoelectriccoupling assembly in accordance with the present invention. The leadframe 30 has a lead forming pattern 31 to be the electrical wiringpattern section 23. The lead forming pattern 31 has short leads 31 a tobe the short electrical wires 23 a and long leads 31 b to be the longelectrical wires 23 b. Spaces 33 where the lead frame 30 has been cutout are disposed between and on the outsides of the leads 31 a and 31 b.During molding, resin 59 fills the spaces 33 and the lead frame 30 isinsert molded into the main unit 20. Positioning holes 32 forpositioning the lead frame 30 are provided at the four corners of thelead forming pattern 31.

The leads 31 a and 31 b are fine (very narrow). For example, if thepitch at which the optical fibers 11 are arranged is 250 μm, then thewidths of the leads 31 a and 31 b will be approximately 50 μm.Consequently, it is difficult to ensure the shear strength of theinsert-molded leads. Additionally, the leads 31 a and 31 b are cut inaccordance with the shape of the molded article 20 after the insertmolding process and the cut surfaces of the leads 31 a and 31 b areexposed at the side surface 22 so as to form electrode terminals 36.Since the surface area of the cut surface of each electrode terminal 36is only the product of the lead thickness and the lead width, there isthe possibility that poor electrical connections would result in thecompleted photoelectric coupling assembly if these cut surfaces alonewere used as contacts.

Therefore, in a photoelectric coupling assembly in accordance with thisembodiment, the leads 31 a and 31 b are each configured and arranged tohave a first surface that is exposed at the front surface 21 of themolded article 20 and electrically connected to the photoelectricconversion element and a second surface that is exposed at a sidesurface 22 of the molded article 20, the side surface 22 beingcontiguous with the front surface 21. Additionally, by providing each ofthe leads 31 a and 31 b with a wide section 34 having a width W1 that iswider than the width W0 at the front surface 21 of the molded article20, an engaging portion is formed that has a width that increases in adirection away from the front surface 21 of the molded article 20. Theleads 31 a and 31 b are insert molded into the front surface 21 of themolded article 20 such that at least a portion of the engaging portionof each is contained inside the resin 20 a forming the molded article20. The leads 31 a and 31 b are also cut from the lead frame 30 suchthat an end face of each (which constitutes a portion of each) isexposed at the side surface 22 of the molded article 20, which iscontiguous with the front surface 21.

FIGS. 4A and 4B are cross sectional views showing examples of leads usedin a photoelectric coupling assembly in accordance with the presentinvention and FIGS. 5A and 5B are cross sectional views showing theinsert molded states of the leads. FIGS. 4A and 5A show a lead 31 a or31 b having a trapezoidal cross sectional shape. The bottom side of thetrapezoid has a larger width than the top side and constitutes the widesection 34. Thus, the entire lead 31 a or 31 b forms the engagingportion 37. The top side of the insert molded lead 31 a or 31 b isexposed from the resin 20 a, and a portion of the engaging portion 37 isembedded in the resin 20 a. In this way, the lead 31 a or 31 b isreliably insert molded into the front surface 21 of the molded article20.

FIGS. 4B and 5B show a lead 31 a or 31 b having a hexagonal crosssectional shape. The wide section 34 is provided in the middle such thatthe portion from the front surface 21 to the middle corms the engagingportion 37. The top side of the insert molded lead 31 a or 31 b isexposed from the resin 20 a, and a portion of the engaging portion 37 isembedded in the resin 20 a. In this way, the lead 31 a or 31 b isreliably insert molded into the front surface 21 of the molded article20.

The engaging portion of the lead 31 a or 31 b shown in FIG. 4A can beformed easily by, for example, forming a mask film on one side of a thincopper plate and etching the copper plate from one side. The engagingportion of the lead 31 a or 31 b shown in FIG. 4B can be formed easilyby, for example, forming a mask film on both sides of a thin copperplate and etching the copper plate from both sides.

It is preferred to apply plating onto the surface of the leads 31 a and31 b after insert molding in preparation for wire bonding. FIGS. 6A and6B show cross sectional views of each of the leads 31 a or 31 b shown inFIGS. 4 and 5 with a plating 35 applied to the surface thereof. Theplating 35 comprises a layer of nickel (Ni) (applied first) and a layerof gold (Au) (applied second) that are applied to the surface of thelead 31 a or 31 b with a non-electrolytic plating method.

It is also acceptable for the lead to be configured such that athickness thereof varies. FIG. 7 is a longitudinal cross sectional viewof a molded article 20 of a photoelectric coupling assembly 10. Thecross section lies in a plane that is parallel to an optical fiberinsertion hole 24 and includes a lead 31 a or 31 b. The thickness T1 ofthe top and bottom end sections of the lead 31 a or 31 b is larger thanthe thickness T0 of the general section such that the electrode terminal36 exposed on the side surface 22 of the molded article 20 is larger.Increasing the thickness of the lead 31 a or 31 b in at the top andbottom in this way makes the lead 31 a or 31 b less likely to becomedetached from the molded article 20 when a vertical force (upward ordownward force) acts on the lead 31 a or 31 b. The increased thicknessalso makes it easier to accomplish wire bonding and enablesthree-dimensional wiring to be accomplished in a reliable manner,thereby increasing the degree of freedom with respect to packagingconfigurations. Thus, when the photoelectric coupling assembly 10 ismounted on a substrate (not shown), the end faces of the leads 31 a and31 b, i.e., the electrode terminals 36, contact the terminals of thesubstrate in a reliable manner.

The thickness variation of the lead can be formed by etching or plating.When the thickness variation is formed by etching, half etching isapplied to the lead frame such that the portions other than the endsections of the leads 31 a and 31 b are made to be thinner.

FIGS. 8A and 8B are cross sectional views showing other examples ofleads used in a photoelectric coupling assembly in accordance with thepresent invention. The lead 31 a or 31 b shown in FIG. 8A is configuredto have a narrow section 60 having a width W2 that is smaller than thewidth W0 at the surface 30 a of the lead frame 30. The lead 31 a or 31 bshown in FIG. 8B has a bellows-like cross sectional shape. In eithercase, an engaging portion 37 whose width increases in a direction awayfrom the front surface 21 is obtained. The method of manufacturing theleads shown in FIGS. 8A and 8B is the same as the method ofmanufacturing the leads shown in FIG. 4.

FIGS. 9A and 9B are frontal views showing other examples of leads usedin a photoelectric coupling assembly in accordance with the presentinvention as seen from the front surface 21 of the molded article 20(first surface of the lead). It is acceptable for the width of the firstsurface to vary with respect to a direction perpendicular to the width.In the example shown in FIG. 9A, the leads 31A are arranged in the frontsurface 21 of the molded article 20 with a prescribed spacing betweenone another and the optical fiber insertion holes 24 are providedin-between the leads 31A. Each of the leads 31A is configured such thatthe width thereof at the front surface 21 varies as one moves along adirection perpendicular to the widthwise direction in the plane of thefront surface 21. More specifically, each of the leads 31A has a widesection D1 at an upper side and a wide section D2 at a lower side alongsaid perpendicular direction (vertical direction in FIG. 9).Additionally, each lead 31A has a narrow section D3 at an intermediateportion along the vertical direction. Conversely, in the example shownin FIG. 9B, each of the leads 31B is configured to have a narrow sectionD4 at an upper side and a narrow section D5 at a lower side along saidperpendicular direction (vertical direction in FIG. 9). Additionally,each lead 31B has a wide section D6 at an intermediate portion along thevertical direction.

Configuring the leads 31B such that the widths thereof vary as one movesalong a direction perpendicular to the width of the lead 31B in theplane of the lead surface makes the leads 31B less likely to becomedetached from the molded article 20 when a force acts on a lead 31B in adirection perpendicular to the widthwise direction of the lead 31B inthe plane of the lead surface. It is acceptable for the variation of thelead width to be either continuous or discontinuous. A lead having avaried width can be fabricated, for example, by etching.

A mold used in a manufacturing method for a photoelectric couplingassembly in accordance with the present invention will now be explained.FIG. 10 is a cross sectional view illustrating a photoelectric couplingassembly being insert molded in accordance with an embodiment of amanufacturing method for a photoelectric coupling assembly in accordancewith the present invention. The mold 50 has an upper die 51 and a lowerdie 52. When the upper and lower dies 51 and 52 are joined together, acavity 53 is formed inside for forming the main unit 20 of thephotoelectric coupling assembly 10. A second slide core 56 is positionedon the frontward side (leftward side in FIG. 10) of the upper and lowerdies 51 and 52 with positioning pins 57 such that it faces toward afirst slide core 55. The second slide core 56 forms a front surface 21on the molded article 20 from which the distal ends 11 a of the opticalfibers 11 are exposed.

The first slide core 55 has a plurality of core pins 54 for forming theinsertion holes 24 (through which the optical fibers 11 will be passed)in the molded article 20 and is inserted between the upper and lowermolds 51 and 52. A protruding part 58 for adjusting the height of thefirst slide core 55 is fitted inside a middle portion of the lower die52 such that the vertical position thereof can be adjusted. Theprotruding part 58 is arranged to adjust the height of the first slidecore 55 by supporting the first slide core 55 from underneath. Theprotruding part 58 also forms an adhesive injection port through whichan adhesive is injected to fasten the optical fiber 11 inside thephotoelectric coupling assembly.

A manufacturing method for a photoelectric coupling assembly inaccordance with the present invention will now be explained. In thismanufacturing method, leads each of which has an engaging portion andsupplies electricity to a photoelectric conversion element arrangedfacing toward the respective optical fiber are insert molded into afront surface and a side surface, which is contiguous with respect tothe front surface, of the molded article which is configured to haveoptical fibers passed there-through such that the distal ends of theoptical fibers are exposed at the front surface. A lead frame 30 isinsert molded into the front surface 21 of the molded article 20 suchthat at least a portion of the engaging portion of each lead iscontained inside the resin 20 a that forms the molded article 20 and afirst surface of each lead is exposed at the first surface 21. In thisway, the leads 31 a and 31 b can be prevented from detaching from thefront surface 21 of the molded article 20. Also, the lead frame 30 iscut such that a second surface of each lead 31 a or 31 b is exposed at aside surface 22 of the molded article 20 that is contiguous with thefront surface 21 of the molded article 20. As a result, a threedimensional wiring pattern can be fabricated with ease.

The manufacturing method will now be explained in more detail. As shownin FIG. 10, the mold 50 is set by assembling the two dies 51 and 52 suchthat a cavity 53 for forming the molded article 20 is formed. The leadframe 30 and the second slide core 56 are mounted to the front surfaces51 a and 52 a of the upper and lower dies 51 and 52 and are positionedthere by the positioning pins 57. The height of the protruding part 58is adjusted to a prescribed height and the first slide core 55 isinserted. The first slide core 55 is positioned by inserting the distalend of the core pin 54 into a core pin positioning hole 56 b provided inthe second slide core 56. Then, resin 20 a is injected into the cavity53 inside the mold 50 and the lead frame 30 is insert molded so as toform the molded article 20. When this is done, as described previously,the wide sections 34 of the leads 31 a and 31 b are contained inside theresin 20 a.

When the resin 20 a is injected and the insert molding of the lead frame30 has been completed, the first slide core 55 and the second slide coreare moved away from each other and the molded article 20 is removed fromthe mold 50. Next, the lead frame 30 insert molded in the front surface21 of the molded article 20 is cut in accordance with the size of thefront surface 21. The end faces exposed at the side surface 22 are thenpolished and plated with nickel followed by gold so as to form electrodeterminals 36. Finally, the photoelectric conversion unit 40 is mountedto the front surface 21 of the molded article 20 such that the activelayer 42 of the photoelectric conversion element 41 is positioneddirectly in front of the optical fiber insertion holes 24 and theelectrodes 43 contact the electrical wiring pattern section 23, i.e.,the leads 31 a and 31 b. By manufacturing the photoelectric couplingassembly 10 in this manner, the front surface 21 of the main unit 20 isformed to be slanted and the transmission properties can be improved.

As described above, in a photoelectric coupling assembly andmanufacturing method thereof in accordance with the present invention,engaging portions are provided in the cross sections of the leadsserving to electrically connect to the photoelectric conversion unit andthe leads are insert molded into the front surface of the moldedarticle. The leads are formed such that at least a portion of theengaging portion is contained inside the resin of the molded article. Asa result, the resin can prevent the leads from becoming detached afterthe leads are insert molded. Also, since a portion of each of the leadsis arranged such that it is exposed at a side surface that is contiguouswith the front surface of the molded article, a three-dimensionalelectrical wiring pattern can be formed easily and reliably.

A photoelectric coupling assembly and manufacturing method thereof inaccordance with the present invention can be used as a photoelectriccoupling assembly and a manufacturing method for a photoelectriccoupling assembly that serves to connect a plurality of optical fiberspassed through insertion holes provided in a molded article to aphotoelectric conversion unit provided on a front surface of the moldedarticle such that it faces the insertion holes.

While this invention has been described in connection with what ispresently considered to be the most practical and preferred embodiments,the invention is not limited to the disclosed embodiments, but on thecontrary, is intended to cover various modifications and equivalentarrangements included within the spirit and scope of the appendedclaims.

The entire disclosure of Japanese Patent Application No. 2006-284845filed on Oct. 19, 2006 including specification, claims, drawings, andsummary are incorporated herein by reference in its entirety.

1. A method of manufacturing a photoelectric coupling assemblycomprising: forming a molded article having a main unit made of resinhaving an optical fiber insertion hole configured and arranged to havean optical fiber inserted there-through, the main unit having a frontsurface and a side surface that is contiguous with the front surface,the forming of the molded article including insert molding in the mainunit a lead frame such that a first surface of the lead frame is exposedat the front surface of the main unit thereby defining a plurality ofleads that includes an engaging portion having a width that increases ina direction away from the front surface with at least a portion of theengaging portion being contained inside the resin of the main unit;cutting the lead frame so that a second surface of the leads are exposedat the side surface of the main unit; and mounting a photoelectricconversion unit to the front surface of the molded article, thephotoelectric conversion unit including electrodes and a photoelectricconversion element having an active layer such that the active layer ofthe photoelectric conversion element is positioned directly in front ofthe optical fiber insertion holes and the electrodes contact the leads.2. The method of manufacturing a photoelectric coupling assembly recitedin claim 1, further comprising etching the engaging portion in the leadframe.
 3. The method of manufacturing a photoelectric coupling assemblyrecited in claim 1, wherein forming the lead frame such that a thicknessof the lead frame varies along at least one direction of the lead frame.4. The method of manufacturing a photoelectric coupling assembly recitedin claim 3, wherein forming of the lead frame is performed such that avariation in the thickness of the lead frame is formed by etching. 5.The method of manufacturing a photoelectric coupling assembly recited inclaim 3, wherein forming of the lead frame is performed such thatvariation in the thickness of the lead frame is formed by applyingplating.
 6. The method of manufacturing a photoelectric couplingassembly recited in claim 1, wherein forming of the lead frame isperformed such that a width of the first surface varies with respect toa direction perpendicular to the width of the first surface.